Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks () and Higgs bosons (). The analysis is based on data collected at a center-of-mass energy of 13Â TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of . No significant excess above the background prediction is observed. Upper limits on the branching fractions () of the top quark decaying to a Higgs boson and an up () or charm () quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95%Â confidence level upper limits are found to be 0.019% (0.031%) for and 0.073% (0.051%) for . These are the strictest upper limits yet determined.